Utilization of moisture in hermetically sealed solid electrolytic capacitors and capacitors made thereof

ABSTRACT

A method for forming a hermetically sealed capacitor including: forming an anode; forming a dielectric on the anode; forming a conductive layer on the dielectric thereby forming a capacitive element; inserting the capacitive element into a casing; electrically connecting the anode to an exterior anode connection; electrically connecting the cathode to an exterior cathode connection; filling the casing with an atmosphere comprising a composition, based on 1 kg of atmosphere, of at least 175 g to no more than 245 g of oxygen, at least 7 g to no more than 11 g of water, at least 734 grams to no more than 818 grams of nitrogen and no more than 10 grams of a minor component; and hermetically sealing the casing with the atmosphere with the capacitive element contained in the casing.

BACKGROUND

The present invention is specific to an improved capacitor and method ofmaking an improved capacitor. More specifically, the present inventionis directed to a method of manufacturing a hermetically sealed capacitorwith improved performance.

Hermetically sealed capacitors have found widespread use in applicationswhere environmental conditions are detrimental to capacitor performance.In general, a hermetically sealed capacitor comprises a capacitiveelement comprising a valve metal anode with a dielectric thereon and aconductive layer on the dielectric. The capacitive element is thenhermetically sealed in a casing. Whereas wet type hermetically sealedcapacitors utilize an electrolyte solution as the cathode conductor,hermetically sealed solid electrolytic capacitors use a solid conductor,such as MnO₂ or intrinsically conducting polymer, as the cathodeconductor. In recent years intrinsically conductive polymers such aspoly 3,4-ethylenedioxythiophene (PEDT) have been used as the preferredcathode conductor in electrolytic capacitors due, in part, to their highelectrical conductivity and benign failure mode. Capacitors made usingin-situ oxidative polymerization or electrochemical polymerization havehigh DC leakage current and have been limited to use in capacitorsintended for applications at lower working voltage. U.S. Pat. No.7,563,290, which is incorporated herein by reference, describes a methodof improving the working voltage of solid electrolytic capacitors bydispersion of prepolymerized conductive polymers.

There has been a long felt desire for improved hermetically sealedcapacitors. In particular, there has been a long felt desire forhermetically sealed solid electrolytic capacitors with lower leakagecurrent and good reliability during the useful life of the capacitor.

SUMMARY

It is an object of the invention to provide an improved method ofmanufacturing a capacitor, and a capacitor obtained thereby withimproved performance.

A particular feature is improved leakage current after aging.

These and other advantages, as will be realized, are provided in amethod for forming a hermetically sealed capacitor.

The method includes:

forming an anode;

forming a dielectric on the anode;

forming a conductive layer on the dielectric thereby forming acapacitive element;

inserting the capacitive element into a casing; electrically connectingthe anode to an exterior anode connection;

electrically connecting the cathode to an exterior cathode connection;

filling the casing with an atmosphere comprising a composition, based on1 kg of atmosphere, of at least 175 g to no more than 245 g of oxygen,at least 7 g to no more than 11 g of water, at least 734 grams to nomore than 818 grams of nitrogen and no more than 10 grams of a minorcomponent; andhermetically sealing the casing with the atmosphere with the capacitiveelement contained in the casing.

Yet another embodiment is provided in a hermetically sealed capacitormade by the process of:

forming an anode;

forming a dielectric on the anode;

forming a conductive layer on the dielectric thereby forming acapacitive element;

inserting the capacitive element into a casing;

electrically connecting the anode to an exterior anode connection;

electrically connecting the cathode to an exterior cathode connection;

filling the casing with an atmosphere comprising a composition, based on1 kg of atmosphere, of at least 175 g to no more than 245 g of oxygen,at least 7 g to no more than 11 g of water, at least 734 grams to nomore than 818 grams of nitrogen and no more than 10 grams of a minorcomponent; andhermetically sealing the casing with the atmosphere with the capacitiveelement contained in the casing.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is a schematic cross-sectional view of an embodiment of theinvention.

FIG. 2 is a schematic cross-sectional view of an embodiment of theinvention.

FIG. 3 is a flow chart representation of an embodiment of the invention.

DESCRIPTION

The instant invention is directed to an improved hermetically sealedsolid electrolytic capacitor and an improved method of manufacturing ahermetically sealed solid electrolytic capacitor. More specifically, thepresent invention is directed to a method of hermetically sealing asolid electrolytic capacitor under specific atmospheric conditions whichprovide an unexpected improvement in aging process and electriccharacteristics of finished capacitors.

The invention will be described with reference to the figures which forman integral, non-limiting, part of the specification. Throughout thevarious figures similar elements will be numbered accordingly.

An embodiment of a hermetically sealed capacitor of the presentinvention will be described with reference to FIG. 1. In FIG. 1, ahermetically sealed capacitor is represented in schematiccross-sectional view at 100. The capacitor, comprises an anode, 10,which is preferably a monolithic anode body comprising a valve metal. Ananode wire, 12, extends from the anode body and can be attached to theanode body by welding or embedded in the anode body by compression. Adielectric, 14, is on the surface of the anode body and preferably atleast partially encases the anode body. A conductive layer, 16, whichfunctions as the cathode, is on the surface of the dielectric of theanode body and preferably at least partially encases the dielectriclayer. As would be realized, the anode and cathode separated by adielectric form the capacitive element. Additional conductive layers,17, are preferably employed to provide an adequate interface forsubsequent electrical connections. The additional conductive layerspreferably include layers comprising carbon, silver, copper, nickel orother conductive materials either in a binder or as a layer of depositedmetal and may include multiple layers. The deposited metal layers can beprovided by vapor deposition, electroplating or electroless plating.

The capacitive element is hermetically sealed in a casing, 32, and inone embodiment a non-conducting case. The cathode is in electricalcontact with a cathode trace, 20. The cathode and cathode trace can beelectrically attached by a conductive adhesive or by welding. The anodewire is in electrical contact with an anode trace, 22, preferablythrough an anode lead element, 18, between the lead wire and the anodetrace. An external cathode connection, 28, is in electrical contact withthe cathode trace, 20, by a connector, 24. An external anode connection,30, is in electrical contact with the anode trace, 22, by a connector,26. A cap, 36, is secured to the casing by a hermetic seal, 38.

Another embodiment of a hermetically sealed solid electrolytic capacitorof the present invention will be described with reference to FIG. 2. InFIG. 2, a hermetically sealed capacitor is represented in schematiccross-sectional view at 101. The capacitor, comprises an anode, 110,which is preferably a monolithic anode body comprising a valve metal. Ananode wire, 112, extends from the anode body and can be attached to theanode body for example by welding, or embedded in the anode body bycompression. A dielectric, 114, is on the surface of the anode body andpreferably at least partially encases the anode body. A conductivelayer, 116, which functions as the cathode, is on the surface of thedielectric of the anode body and preferably at least partially encasesthe dielectric layer. As would be realized, the anode and cathodeseparated by a dielectric form the capacitive element. Additionalconductive layers, 117, are preferably employed to provide an adequateinterface for subsequent connection to the casing and the cathode leadwire, 124. The additional conductive layers preferably include layerscomprising carbon, silver, copper, nickel or other conductive materialseither in a binder or as a layer of deposited metal and may includemultiple layers. The deposited metal layers can be provided by vapordeposition, electroplating or electroless plating.

The capacitive element is hermetically sealed in a casing, 132, which inone embodiment is a conductive casing. The internal connection material,126, which connects the conductive layers, 117, to cathode lead wire,124, can be either an internal solder or an electrically conductiveadhesive. The cathode lead, 124, is attached to the casing or it mayextend into the internal connection material, 126. An external anodelead, 118, is connected, preferably by welding, to the anode wire, 112.The external anode lead extends out of the casing. A positive seal, 128,contains at least a portion of the external anode lead and/or the anodewire. An edge seal, 131, hermetically seals the casing with the capmaterial, 130. While not limited thereto, the external anode lead andcathode lead are preferably nickel. Although many metallic and glass tometal seal materials can be used to provide hermetic sealing of thecasing, the positive seal material and the edge sealing material arepreferably solder.

It has been surprisingly determined that performance of a hermeticallysealed solid electrolytic capacitor can be improved by hermeticallysealing in a defined atmosphere comprising air and moisture within apredetermined range. This is in direct contrast to expectations in theart since hermetic seals typically prefer those that exclude moistureand oxygen. The edge seal is applied and a hermetic seal formed in anatmosphere comprising a composition, based on 1 Kg of atmosphere, of atleast 175 g to no more than 245 g of oxygen, at least 7 g to no morethan 11 g of water, at least 734 grams to no more than 818 grams ofnitrogen and no more than 10 grams of a minor component wherein theminor component preferably comprises gases selected from the groupconsisting of carbon dioxide, carbon monoxide, inert gases, methane,hydrogen, ammonia and nitrous oxides. More preferably, the atmospherehas a composition with at least 8 grams to no more than 10 grams ofwater per Kg of atmosphere.

The method of manufacturing the hermetically sealed solid electroylticcapacitor will be described with reference to FIG. 3.

In FIG. 3, an anode is formed at 200. In a preferred embodiment theanode is formed from a powder which is compressed to form a monolithicbody. In another embodiment the anode is a foil which is optionally, andpreferably, etched to increase surface area. The shape and dimension ofthe anode is not particularly limited herein. In the case of acompressed powder anode an anode wire can be attached to the anode aftercompression, such as by welding, or the anode wire can be inserted intothe powder and the powder compressed around the anode wire therebyforming an anode with an anode wire embedded in the anode and extendingtherefrom.

A dielectric is formed on the anode at 202. While not limited thereto, apreferred dielectric is an oxide of the anode material. This ispreferred primarily for manufacturing convenience. Preferably, thedielectric is an oxide of Al, W, Ta, Nb, Ti, Zr and Hf with Al₂O₃, Ta₂O₅and Nb₂O₅ being most preferred. The method of forming the dielectric isnot limited herein. Anodization of a valve metal to form a dielectric iswell understood in the art and described in detail in U.S. Pat. Nos.7,678,259; 7,248,462; 6,755,959; 6,652,729; 6,480,371; 6,436,268;6,346,185; 6,267,861; 6,235,181; 5,716,511; 5,185,075 and 4,812,951. Onemethod for anodization employs anodizing solutions having a watercontent below approximately 30% in combination with alkanol amine,phosphoric acid and an organic solvent. Monoethanol amine, diethanolamine, triethanol amine, ethyl diethanolamine, diethyl ethanolamine,dimethyl ethanolamine and dimethyl ethoxy ethanolamine (dimethyl aminoethoxy ethanol) are mentioned as alkanol amines. Ethylene glycol,diethylene glycol, polyethylene glycol 300 and tetraethylene glycoldimethyl ether, are mentioned as solvents. It is generally desirable toconduct the anodizing at temperatures below about 50° C., preferablywithin a pH range of 4-9 which can be adjusted with phosphoric acid ifdesired.

A cathode is formed on the dielectric at 204. The cathode is a conductorpreferably comprising at least one of manganese dioxide or aintrinsically conductive polymeric material as known in the art. Thecathode may include multiple layers wherein adhesion layers are employedto improve adhesion between the conductor and the termination.Particularly preferred adhesion layers include carbon, silver, copper,or another conductive material in a binder or a metalized layer such asnickel or silver. Conductive polymeric materials may be employed as acathode material. Particularly preferred intrinsically conductivepolymers include polypyrrole, polyaniline, polythiophene and theirderivatives. A particularly preferred conductive polymer is poly3,4-ethylenedioxythiophene (PEDT). PEDT can be made by in situpolymerization of EDT monomer such as Clevius M V2 which is commerciallyavailable from Hereaus Clevious with an oxidizer such as ferric tosylatesolution available as Clevios® C from Hereaus Clevios. The applicationand polymerization of heterocyclic conductive polymers such aspolypyrrole, polyaniline, polythiophene and their derivatives is widelydescribed and well known to those of skill in the art. Additionalconductive layers preferably include layers comprising carbon, silver,copper, nickel or other conductive materials either in a binder or as alayer of deposited metal and may include multiple layers are preferablydeposited on the polymeric cathode layer to improve subsequent adhesion.

The capacitive element, which comprises an anode and cathode with adielectric there between, is inserted into a casing at 206. The casingpreferably has a cavity within which the capacitive couple resides. Theanode wire is electrically connected to an external anode connection andthe cathode is electrically connected to an external cathode connection.In one embodiment the casing comprises connectors between internaltraces and external connections wherein the capacitor is electricallyconnected to the internal traces by welding, conductive adhesive or thelike.

An atmosphere is provided at 208 wherein the atmosphere comprises acomposition, based on 1 kg of atmosphere, of at least 175 g to no morethan 245 g of oxygen, at least 7 g to no more than 11 g of water andmore preferably at least 8 g to no more than 10 g of water, at least 734grams to no more than 818 grams of nitrogen and no more than 10 grams ofminor components wherein the minor components preferably comprise gasesselected from the group consisting of carbon dioxide, carbon monoxide,inert gases, methane, hydrogen, ammonia and nitrous oxides. Morepreferably, the atmosphere comprises at least 200 g to no more than 220g of oxygen per kg of atmosphere. The case is hermetically sealed in theprovided atmosphere at 210.

It is preferred that the capacitors be tested at 212. One portion of thetesting is a burn-in wherein the capacitor is subjected to 1.0 to 1.5times of the rated voltage at a temperature of 50° C. to 150° C. Morepreferably, the capacitor is aged at 1.2 to 1.4 times of the ratedvoltage at a temperature of 75° C. to 125° C.

The anode is a conductor preferably selected from a metal or aconductive metal oxide. More preferably the anode comprises a mixture,alloy or conductive oxide of a valve metal preferably selected from Al,W, Ta, Nb, Ti, Zr and Hf. Most preferably, the anode comprises at leastone material selected from the group consisting of Al, Ta, Nb and NbO.

The anode wire is most preferably constructed of the same material asthe anode. The anode wire can be welded onto the anode surface underprotective atmosphere or inserted into a powder prior to compression ofthe powder to form a porous anode body.

The dielectric is a non-conductive layer which is not particularlylimited herein. The dielectric may be a metal oxide or a ceramicmaterial. A particularly preferred dielectric is the oxide of an anodemetal due to the simplicity of formation and ease of use.

The casing can be a metal or a ceramic. The casing may include a singlelayer or multiple layers with aluminum nitride, aluminum oxide, siliconoxide, magnesium oxide and calcium oxide being mentioned as exemplarymaterials. Conductive materials, such as a metal, are mentioned asexemplary for demonstration of the invention. The metal casing mayinclude a surface coating on the interior and/or exterior thereof toincrease conductivity or to improve solderability. A conductive casingmay be constructed of brass with a solder coating, such as a Sn/Pbplating, on the inside and outside of the casing. The width, length anddepth of the casing are selected for the application and are nototherwise limited herein. It would be readily apparent that a minimalsize consistent with the application is preferred. In general, a lengthof 1 to about 25 millimeters with a width, or diameter in the case of acylindrical case, of 0.5 to 10 millimeters is mentioned as beingsuitable for demonstration of the invention.

The capacitive element can be electrically connected to the casing inany manner known in the art. In one embodiment various surfaces of thecasing may comprise interior conductive traces, or conductive pads, thatare electrically connected to exterior conductive traces or conductivepads. The capacitive element is then electrically connected to theinterior conductive traces or conductive pads and the exteriorconductive traces or conductive pads are connected to a circuit trace toadd capacitance to a circuit. The conductive trace or conductive pad isa conductive material without limit. Copper, nickel, silver, zinc, tin,palladium, lead, aluminum, molybdenum, titanium, iron, zirconium,tungsten, magnesium and alloys thereof are mentioned as suitable fordemonstration of the instant invention. Copper, copper alloys; such ascopper-zirconium, copper-magnesium, copper-zinc or copper-iron; nickel,nickel alloys; such as nickel-iron; and gold coated metal layers areparticularly suitable for demonstration of the invention. An inkcontaining the conductor may be deposited in a predetermined pattern,such as by ink jet printing, to form the conductive traces or conductivepads.

The internal conductive traces or conductive pads may be electricallyconnected to external conductive traces or pads thereby allowing thehermetically sealed capacitor to be mounted on a surface. The internalconductive traces or conductive pads and external conductive traces orconductive pads are electrically connected by any method known in theart. The conductive material may extend through the casing or may be inthe form of pins, pads, sheets, etc. The external conductive traces orconductive pads are preferably as thin as possible to minimize totalsize of the hermetically sealed capacitor with the proviso that adequateconductivity is achieved.

EXAMPLES

A series of identical capacitive elements were prepared with acylindrical tantalum anode with a diameter of 5.2 mm and a length of10.7 mm comprising a tantalum wire lead. A tantalum pentoxide dielectricwas prepared as taught in accordance with U.S. Pat. No. 5,716,511. Acathode layer was formed using prepolymerized PEDT dispersion, Clevios Kavailable from Hereaus Clevios as taught in U.S. Pat. No. 7,563,290.Carbon containing and silver containing layers were coated on the PEDTlayers for adhesion. Each capacitive couple was placed in a nickelcoated brass casing with an outside diameter of 7.1 mm, a height of 16.5mm and a wall thickness of 0.30 mm. Using a Sn62.5/Pb26.1/Ag1.4 solderan electrically conductive bond is formed between the cathode and thecasing. The samples were separated for separate treatment. One set ofsamples were directly sealed right after the bonding between the cathodeand the casing by solder. An inventive set of samples was treated for 24hours in an air atmosphere maintained at about 50% relative humidity at23° C. or about 8.8 grams of water per kilogram of air atmosphere afterbonding between the cathode and the casing by solder. Both sample setswere hermetically sealed by an edge seal and a positive seal bothcomprising Sn60/Pb40 solder. The entire population of sealed capacitorswas heated to a temperature of 125° C. A subpopulation of each set wasmaintained with no voltage and another subpopulation was maintained a ⅔rated voltage, which was 40 volts, for a period of time as set forth inthe tables. The capacitance in microfarads (CAP), dissipation factor inpercent (DF), equivalent series resistance in ohms (ESR) and DC leakagecurrent in microamperes (LKG) were measured and recorded. CAP and DFwere measured with an AC signal at 120 Hz while ESR was measured at 100KHz, as well known in the industry. The DC leakage was measured withrated voltage of 60V and a charging time of less than 300 seconds. Theinitial results are indicated in Table 1, the results after 23 hours arerecorded in Table 2 and the results after 100 hours are recorded inTable 3.

As indicated in the Tables, the capacitor prepared with a moist seal hadhigher capacitance initially and much lower leakage after aging testing.In particular, the leakage current of the capacitors was improvedconsiderably after the burn-in.

TABLE 1 125° C. 125° C. and ⅔ NO VOLTAGE RATED VOLTAGE INITIAL INITIALLKG LKG CAP DF ESR 60 V CAP DF ESR 60 V DRY SEAL DRY SEAL 83.9 2.7 0.061.03 83.9 2.7 0.07 0.97 83.5 2.8 0.06 1.24 84.6 2.7 0.05 0.93 83.3 2.90.07 1.08 83.8 3.5 0.05 1.14 84.4 2.7 0.06 1.11 84.7 3.4 0.06 1.21 84.72.7 0.05 1.00 NONE MOIST SEAL MOIST SEAL 93.9 3.7 0.06 0.55 95.6 3.30.05 0.58 94.7 3.4 0.05 0.55 93.3 3.5 0.05 0.59 95.2 3.4 0.06 0.55 94.43.5 0.05 5.56 94.3 3.5 0.05 0.56 94.2 3.4 0.04 5.66 94.7 3.4 0.05 0.57NONE

TABLE 2 125° C. 125° C. and ⅔ NO VOLTAGE RATED VOLTAGE 23 HRS 23 HRS LKGLKG CAP DF ESR 60 V CAP DF ESR 60 V DRY SEAL DRY SEAL 84.8 3.0 0.0619.98 84.1 3.0 0.06 9.18 84.3 3.0 0.05 69.12 84.6 2.9 0.05 0.95 84.6 3.00.05 12.71 84.1 3.8 0.05 1.29 84.8 3.1 0.05 144.48 85.8 3.9 0.05 1.3085.0 3.2 0.04 13.93 NONE MOIST SEAL MOIST SEAL 93.0 3.8 0.05 18.24 94.73.2 0.05 1.86 93.8 3.7 0.05 1.19 91.9 3.6 0.06 0.61 94.0 3.6 0.07 1.8393.2 3.4 0.06 3.39 93.5 3.7 0.05 0.79 92.6 3.4 0.04 1.04 93.6 3.6 0.050.98 NONE

TABLE 3 125° C. 125° C. and ⅔ NO VOLTAGE RATED VOLTAGE 100 HRS 100 HRSLKG LKG CAP DF ESR 60 V CAP DF ESR 60 V DRY SEAL DRY SEAL 84.1 2.9 0.06259.78 83.0 2.7 0.06 74.47 83.5 3.0 0.05 378.50 83.4 2.6 0.05 6.06 83.83.0 0.05 87.65 83.8 3.5 0.05 41.34 84.2 3.2 0.06 50.40 85.2 3.7 0.0616.93 84.0 3.0 0.05 113.59 NONE MOIST SEAL MOIST SEAL 91.4 3.8 0.06 9.6093.1 3.1 0.06 0.98 92.3 3.5 0.06 4.34 90.3 3.4 0.06 3.23 92.7 3.5 0.063.93 91.5 3.2 0.06 4.19 92.1 3.6 0.05 4.80 91.0 3.1 0.05 2.17 92.1 3.50.05 6.75 NONE

The invention has been described with reference to preferred embodimentswithout limit thereto. One of skill in the art would readily appreciateadditional embodiments and improvements which are within the scope ofthe invention as more specifically set forth in the claims appendedhereto.

The invention claimed is:
 1. A method for forming a hermetically sealedcapacitor comprising: forming an anode; forming a dielectric on saidanode; forming a cathode by forming a solid conductive layer on saiddielectric thereby forming a capacitive element; inserting saidcapacitive element into a casing; electrically connecting said anode toan exterior anode connection; electrically connecting said cathode to anexterior cathode connection; filling said casing with an atmospherecomprising a composition, based on 1 kg of atmosphere, of at least 175 gto no more than 245 g of oxygen, at least 7 g to no more than 11 g ofwater, at least 734 grams to no more than 818 grams of nitrogen and nomore than 10 grams of a minor component; allowing a time sufficient toallow said polymeric cathode to reach equilibrium; and hermeticallysealing said casing with said atmosphere with said capacitive elementcontained in said casing.
 2. The method for forming a hermeticallysealed capacitor of claim 1 wherein said minor component comprises gasesconsisting essentially of argon, carbon dioxide, carbon monoxide, inertgas, methane, hydrogen, ammonia and nitrous oxides.
 3. The method forforming a hermetically sealed capacitor of claim 1 wherein saidatmosphere comprises at least 200 g to no more than 220 g of oxygen. 4.The method for forming a hermetically sealed capacitor of claim 1wherein said atmosphere comprises at least 8 g to no more than 10 g ofwater.
 5. The method for forming a hermetically sealed capacitor ofclaim 1 wherein said anode comprises a valve metal or a conductive oxideof said valve metal.
 6. The method for forming a hermetically sealedcapacitor of claim 5 wherein said valve metal is selected from Al, W,Ta, Nb, Ti, Zr and Hf.
 7. The method for forming a hermetically sealedcapacitor of claim 5 wherein said anode comprises a material selectedfrom the group consisting of Ta, Nb and NbO.
 8. The method for forming ahermetically sealed capacitor of claim 1 wherein said dielectric is anoxide of an anode material.
 9. The method for forming a hermeticallysealed capacitor of claim 8 wherein said dielectric is selected fromNb₂O₅, Ta₂O₅ and Al₂O₃.
 10. The method for forming a hermetically sealedcapacitor of claim 1 wherein said conductive layer comprises at leastone material selected from manganese dioxide and a conductive polymer.11. The method for forming a hermetically sealed capacitor of claim 10wherein said conductive polymer is a prepolymerized dispersion ofintrinsically conductive polymer.
 12. The method for forming ahermetically sealed capacitor of claim 10 wherein said conductivepolymer is a polythiophene.
 13. The method for forming a hermeticallysealed capacitor of claim 12 wherein said polythiophene is aprepolymerized dispersion of polythiophene.
 14. The method for forming ahermetically sealed capacitor of claim 12 wherein said polythiophene ispoly 3,4-ethylenedioxythiophene.
 15. The method for forming ahermetically sealed capacitor of claim 14 wherein said poly3,4-ethylenedioxythiophene is a prepolymerized dispersion of poly3,4-ethylenedioxythiophene.
 16. The method for forming a hermeticallysealed capacitor of claim 1 further comprising an anode wire extendingfrom said anode.
 17. The method for forming a hermetically sealedcapacitor of claim 1 wherein at least one of said external anodeconnection or said external cathode connection comprises nickel.
 18. Themethod for forming a hermetically sealed capacitor of claim 1 whereinsaid casing further comprises conducting traces.
 19. The method forforming a hermetically sealed capacitor of claim 1 further comprisingapplying solder between said cathode and said casing.
 20. The method forforming a hermetically sealed capacitor of claim 19 wherein saidexternal cathode lead is in electrical contact with said solder.
 21. Themethod for forming a hermetically sealed capacitor of claim 1 whereinsaid hermetically sealing comprises forming a seal with solder.
 22. Ahermetically sealed capacitor made by the process of: forming an anode;forming a dielectric on said anode; forming a cathode by forming a solidconductive layer on said dielectric thereby forming a capacitiveelement; inserting said capacitive element into a casing; electricallyconnecting said anode to an exterior anode connection; electricallyconnecting said cathode to an exterior cathode connection; filling saidcasing with an atmosphere comprising a composition, based on 1 kg ofatmosphere, of at least 175 g to no more than 245 g of oxygen, at least7 g to no more than 11 g of water, at least 734 grams to no more than818 grams of nitrogen and no more than 10 grams of a minor component;and allowing a time sufficient to allow said polymeric cathode to reachequilibrium; hermetically sealing said casing with said atmosphere withsaid capacitive element contained in said casing.
 23. The hermeticallysealed capacitor of claim 22 wherein said anode comprises a valve metalor a conductive oxide of said valve metal.
 24. The hermetically sealedcapacitor of claim 23 wherein said valve metal is selected from Al, W,Ta, Nb, Ti, Zr and Hf.
 25. The hermetically sealed capacitor of claim 23wherein said anode comprises a material selected from the groupconsisting of Nb and NbO.
 26. The hermetically sealed capacitor of claim22 wherein said dielectric is an oxide of an anode material.
 27. Thehermetically sealed capacitor of claim 26 wherein said dielectric isselected from Nb₂O₅, Ta₂O₅ and Al₂O₃.
 28. The hermetically sealedcapacitor of claim 22 wherein said conductive layer comprises at leastone material selected from manganese dioxide and a conductive polymer.29. The hermetically sealed capacitor of claim 28 wherein saidconductive polymer is a prepolymerized dispersion.
 30. The hermeticallysealed capacitor of claim 28 wherein said conductive polymer is apolythiophene.
 31. The hermetically sealed capacitor of claim 30 whereinsaid polythiophene is poly 3,4-ethylenedioxythiophene.
 32. Thehermetically sealed capacitor of claim 30 wherein said poly3,4-ethylenedioxythiophene is prepolymerized dispersion of poly3,4-ethylenedioxythiophene.
 33. The hermetically sealed capacitor ofclaim 28 wherein said polythiophene is prepolymerized dispersion ofpolythiophene.
 34. The hermetically sealed capacitor of claim 22 whereinsaid minor component comprises gases consisting essentially of argon,carbon dioxide, carbon monoxide, inert gas, methane, hydrogen, ammoniaand nitrous oxides.
 35. The hermetically sealed capacitor of claim 22wherein said atmosphere comprises at least 200 g to no more than 220 gof oxygen.
 36. The hermetically sealed capacitor of claim 22 whereinsaid atmosphere comprises at least 8 g to no more than 10 g of water.37. The hermetically sealed capacitor of claim 22 wherein at least oneof said external anode connection or said external cathode connectioncomprises nickel.
 38. The hermetically sealed capacitor of claim 22wherein said casing further comprises conducting traces.
 39. Thehermetically sealed capacitor of claim 22 further comprising applyingsolder between said cathode and said casing.
 40. The hermetically sealedcapacitor of claim 39 wherein said external cathode lead is inelectrical contact with said solder.
 41. A method for forming ahermetically sealed capacitor comprising: forming an anode; forming adielectric on said anode; forming a solid cathode by forming aconductive layer on said dielectric thereby forming a capacitiveelement; inserting said capacitive element into a casing; electricallyconnecting said anode to an exterior anode connection; electricallyconnecting said cathode to an exterior cathode connection; and after atime sufficient to allow said polymeric cathode to reach equilibriumhermetically sealing said casing with said capacitive element containedin said casing.
 42. The method for forming a hermetically sealedcapacitor of claim 41 wherein said casing comprises a controlledatmosphere comprising at least 175 g to no more than 245 g of oxygen.43. The method for forming a hermetically sealed capacitor of claim 42wherein said controlled atmosphere comprises at least 734 g to no morethan 818 g of nitrogen.
 44. The method for forming a hermetically sealedcapacitor of claim 42 wherein said controlled atmosphere comprises aminor component selected from the group consisting of argon, carbondioxide, carbon monoxide, methane, hydrogen, ammonia and nitrous oxide.45. The method for forming a hermetically sealed capacitor of claim 44wherein said controlled atmosphere comprises no more than 10 g of saidminor component.
 46. The method for forming a hermetically sealedcapacitor of claim 42 wherein said controlled atmosphere comprises atleast 200 g to no more than 220 g of oxygen.
 47. The method for forminga hermetically sealed capacitor of claim 42 wherein said controlledatmosphere comprises at least 8 g to no more than 10 g of water.
 48. Themethod for forming a hermetically sealed capacitor of claim 42 whereinsaid anode comprises a valve metal or a conductive oxide of said valvemetal.
 49. The method for forming a hermetically sealed capacitor ofclaim 48 wherein said valve metal is selected from the group consistingof Al, W, Ta, Nb, Ti, Zr and Hf.
 50. The method for forming ahermetically sealed capacitor of claim 48 wherein said anode comprises amaterial selected from the group consisting of Ta, Nb and NbO.
 51. Themethod for forming a hermetically sealed capacitor of claim 41 whereinsaid dielectric is an oxide of an anode material.
 52. The method forforming a hermetically sealed capacitor of claim 51 wherein saiddielectric is selected from Nb₂O₅, Ta₂O₅ and Al₂O₃.
 53. The method forforming a hermetically sealed capacitor of claim 41 wherein saidconductive layer comprises at least one material selected from manganesedioxide and a conductive polymer.
 54. The method for forming ahermetically sealed capacitor of claim 53 wherein said polythiophene isa prepolymerized dispersion of intrinsically conducting polymer.
 55. Themethod for forming a hermetically sealed capacitor of claim 53 whereinsaid conductive polymer is a polythiophene.
 56. The method for forming ahermetically sealed capacitor of claim 55 wherein said polythiophene ispoly 3,4-ethylenedioxythiophene.
 57. The method for forming ahermetically sealed capacitor of claim 56 wherein said poly3,4-ethylenedioxythiophene is a prepolymerized dispersion of poly3,4-ethylenedioxythiophene.
 58. The method for forming a hermeticallysealed capacitor of claim 41 further comprising an anode wire extendingfrom said anode.
 59. The method for forming a hermetically sealedcapacitor of claim 41 wherein at least one said external anodeconnection or said external cathode connection comprises nickel.
 60. Themethod for forming a hermetically sealed capacitor of claim 41 whereinsaid casing further comprises conducting traces.
 61. The method forforming a hermetically sealed capacitor of claim 60 wherein saidhermetically sealing comprises forming a seal with solder.
 62. Themethod for forming a hermetically sealed capacitor of claim 41 furthercomprising applying solder between said cathode and said casing.
 63. Themethod for forming a hermetically sealed capacitor of claim 62 whereinsaid hermetically sealing comprises forming a seal with additionalsolder.
 64. A hermetically sealed capacitor made by the process of:forming an anode; forming a dielectric on said anode; forming a cathodeby forming a solid conductive layer on said dielectric thereby forming acapacitive element; inserting said capacitive element into a casing;electrically connecting said anode to an exterior anode connection;electrically connecting said cathode to an exterior cathode connection;and after a time sufficient to allow said polymeric cathode to reachequilibrium hermetically sealing said casing with said capacitiveelement contained in said casing wherein said conductive layer is inequilibrium with an atmosphere in said casing.
 65. The hermeticallysealed capacitor of claim 64 wherein said anode comprises a valve metalor a conductive oxide of said valve metal.
 66. The hermetically sealedcapacitor of claim 65 wherein said valve metal is selected from thegroup consisting of Al, W, Ta, Nb, Ti, Zr and Hf.
 67. The hermeticallysealed capacitor of claim 65 wherein said anode comprises a materialselected from the group consisting of Ta, Nb and NbO.
 68. Thehermetically sealed capacitor of claim 64 wherein said atmospherecomprises at least 175 g to no more than 245 g of oxygen.
 69. Thehermetically sealed capacitor of claim 64 wherein said atmospherecomprises at least 734 g to no more than 818 g of nitrogen.
 70. Thehermetically sealed capacitor of claim 64 wherein said atmospherecomprises a minor component selected from the group consisting of argon,carbon dioxide, carbon monoxide, methane, hydrogen, ammonia and nitrousoxide.
 71. The hermetically sealed capacitor of claim 70 wherein saidatmosphere comprises no more than 10 g of said minor component.
 72. Thehermetically sealed capacitor of claim 64 wherein said atmospherecomprises at least 200 g to no more than 220 g of oxygen.
 73. Thehermetically sealed capacitor of claim 64 wherein said atmospherecomprises at least 8 g to no more than 10 g of water.
 74. Thehermetically sealed capacitor of claim 64 wherein said dielectric is anoxide of an anode material.
 75. The hermetically sealed capacitor ofclaim 74 wherein said dielectric is selected from Nb₂O₅, Ta₂O₅ andAl₂O₃.
 76. The hermetically sealed capacitor of claim 64 wherein saidconductive layer comprises at least one material selected from manganesedioxide and a conductive polymer.
 77. The hermetically sealed capacitorof claim 76 wherein said conductive polymer is a prepolymerizeddispersion of intrinsically conducting polymer.
 78. The hermeticallysealed capacitor of claim 76 wherein said conductive polymer is apolythiophene.
 79. The hermetically sealed capacitor of claim 78 whereinsaid polythiophene is poly 3,4-ethylenedioxythiophene.
 80. Thehermetically sealed capacitor of claim 79 wherein said poly3,4-ethylenedioxythiophene is a prepolymerized dispersion of poly3,4-ethylenedioxythiophene.
 81. The hermetically sealed capacitor ofclaim 64 further comprising an anode wire extending from said anode. 82.The hermetically sealed capacitor of claim 64 wherein at least one saidexternal anode connection or said external cathode connection comprisesnickel.
 83. The hermetically sealed capacitor of claim 64 wherein saidcasing further comprises conducting traces.
 84. The hermetically sealedcapacitor of claim 64 further comprising applying solder between saidcathode and said casing.
 85. The hermetically sealed capacitor of claim84 wherein said hermetically sealing comprises forming a seal withsolder.
 86. The hermetically sealed capacitor of claim 85 wherein saidexternal cathode lead is in electrical contact with said solder.